U.S. patent number 5,445,148 [Application Number 08/138,557] was granted by the patent office on 1995-08-29 for intracardiac electrical potential reference catheter.
This patent grant is currently assigned to Medtronic CardioRhythm. Invention is credited to Richard Jaraczewski, Scott West.
United States Patent |
5,445,148 |
Jaraczewski , et
al. |
August 29, 1995 |
Intracardiac electrical potential reference catheter
Abstract
An intracardiac electrical potential reference catheter includes
a proximal shaft section in a distal flexible tip section. The
flexible tip section shaped in a geometry suitable for performing
intracardiac mapping and includes a plurality of electrode axially
spaced-apart thereon. The shaft section is formed from a polymeric
material and includes a reinforcement layer, typically a stainless
steel braid. The flexible tip section is also formed from a
polymeric material and is free from any braided reinforcement. A
core wire is attached to a proximal housing on the catheter at one
end and to a distal electrode tip at the other end. In this way,
the torque is transmitted along the length of the catheter by both
the reinforced shaft and separately by the core wire.
Inventors: |
Jaraczewski; Richard
(Livermore, CA), West; Scott (Tracy, CA) |
Assignee: |
Medtronic CardioRhythm (San
Jose, CA)
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Family
ID: |
25348350 |
Appl.
No.: |
08/138,557 |
Filed: |
October 15, 1993 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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866763 |
Apr 10, 1992 |
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Current U.S.
Class: |
600/374;
600/395 |
Current CPC
Class: |
A61M
25/0133 (20130101); A61B 5/6855 (20130101); A61B
5/287 (20210101); A61M 25/0141 (20130101); A61B
2562/043 (20130101); A61M 2025/0161 (20130101) |
Current International
Class: |
A61B
5/0408 (20060101); A61B 5/042 (20060101); A61M
25/01 (20060101); A61B 005/04 () |
Field of
Search: |
;128/642,673
;607/119,120,122,123 ;604/264,280,282 ;606/46 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0476807 |
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Mar 1992 |
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EP |
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3642107 |
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Jun 1987 |
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DE |
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Primary Examiner: Cohen; Lee S.
Assistant Examiner: Gilbert; Samuel
Attorney, Agent or Firm: Townsend and Townsend Khourie and
Crew
Parent Case Text
This is a Continuation-in-part of application Ser. No. 07/866,763
filed Apr. 10, 1992, now abandoned.
The present application is related to application Ser. No.
07/866,383 now U.S. Pat. No. 5,318,525, Ser. No. 07/866,683, filed
on the same date as the present application. The disclosures of all
of these co-pending applications are incorporated herein by
reference.
Claims
What is claimed is:
1. An electrical potential reference catheter comprising:
a shaft having a proximal end, a distal end, and a lumen extending
between said ends, wherein the shaft is a polymeric shaft tube
having a braided reinforcement layer;
a flexible tip section having a proximal end, a distal end, and a
lumen extending between said ends, wherein the tip section is a
polymeric tip tube and is fixedly attached at its proximal end to
the distal end of the shaft;
a tip electrode fixedly secured to the distal end of the flexible
tip section;
at least one additional band electrode proximally spaced-apart from
the tip electrode on the flexible tip section;
a proximal connector housing fixedly attached to the proximal end
of the shaft;
whereby said shaft and said tip section provide torque transmission
directly from the housing to the tip electrode;
a single core wire suspended generally coaxially in the lumens of
the shaft and flexible tip section and extending between the
proximal connector housing and the tip electrode and fixedly
connected to both, wherein a distal end of the core wire is
anchored coaxially within the tip electrode;
whereby said core wire provides torque transmission directly from
the housing to the tip electrode; and
means for electrically connecting the electrodes to the proximal
connector housing.
2. An electrical potential reference catheter as in claim 1 wherein
the shaft tube is composed of a material selected from the group
consisting of a polyurethane, a nylon, a polyethylene block
copolymer, and a polyolefin having a durometer from 35D to 75D and
wherein the braided reinforcement layer is a stainless steel
reinforcement braid.
3. An electrical potential reference catheter as in claim 2,
wherein the tip tube is composed of a material selected from the
group consisting of a polyurethane, a nylon, a polyethylene block
copolymer, and a polyolefin having a durometer from 30A to 75A.
4. An electrical potential reference catheter as in claim 3,
wherein the core wire is stainless steel having a diameter from
0.005 in. to 0.025 in.
5. An electrical potential reference catheter as in claim 4,
wherein the core wire has proximal and distal ends, the core wire
being tapered, having a diameter from 0.015 in. to 0.025 in. at its
proximal end and a diameter from 0.005 in. to 0.015 in. at its
distal end.
6. An electrical potential reference catheter as in claim 1,
further comprising a polymeric sheath tube extending into an axial
receptacle in the tip electrode and receiving the core wire in
order to provide electrical insulation of the core wire at the
transition to the tip electrode.
7. An electrical potential reference catheter as in claim 6,
wherein the polymeric sheath tube is composed of a polyimide.
8. An electrical potential reference catheter comprising:
a shaft having a proximal end, a distal end, and a lumen extending
between said ends, wherein the shaft is a polymeric shaft tube
having a braided reinforcement layer;
a flexible tip section having a proximal end, a distal end, and a
lumen extending between said ends, wherein the tip section is a
polymeric tip tube and is fixedly attached at its proximal end to
the distal end of the shaft;
a tip electrode fixedly secured to the distal end of the flexible
tip section;
at least one additional band electrode proximally spaced-apart from
the tip electrode on the flexible tip section;
a proximal connector housing fixedly attached to the proximal end
of the shaft;
whereby said shaft and said tip section provide torque transmission
directly from the housing to the tip electrode;
a core wire extending between the proximal connector housing and
the tip electrode and fixedly connected to both;
whereby said core wire provides torque transmission directly from
the housing to the tip;
a polymeric sheath tube extending into an axial receptacle in the
tip electrode and receiving the core wire in order to provide
electrical insulation of the core wire at the transition to the tip
electrode; and
means for electrically connecting the electrodes to the proximal
connector housing.
9. An electrical potential reference catheter as in claim 8 wherein
the shaft tube is composed of a material selected from the group
consisting of a polyurethane, a nylon, a polyethylene block
copolymer, and a polyolefin having a durometer from 35D to 75D with
a stainless steel reinforcement braid.
10. An electrical potential reference catheter as in claim 9,
wherein the flexible tip tube is composed of a material selected
from the group consisting of a polyurethane, a nylon, a
polyethylene block copolymer, and a polyolefin having a durometer
from 30A to 75A.
11. An electrical potential reference catheter as in claim 10,
wherein the core wire is stainless steel having a diameter from
0.005 in. to 0.025 in.
12. An electrical potential reference catheter as in claim 11,
wherein the core wire has proximal and distal ends, the core wire
being tapered, having a diameter from 0.015 in. to 0.025 in. at its
proximal end and a diameter from 0.005 in. to 0.015 in. at its
distal end.
13. An electrical potential reference catheter as in claim 8,
wherein the polymeric sheath tube is composed of a polyimide.
14. An electrical potential reference catheter comprising:
a shaft having a proximal end, a distal end, and a lumen extending
between said ends, wherein the shaft is a polymeric shaft tube
having a braided reinforcement layer;
a flexible tip section having a proximal end, a distal end, and a
lumen extending between said ends, wherein the tip section is a
polymeric tip tube and is fixedly attached at its proximal end to
the distal end of the shaft;
a tip electrode fixedly secured to the distal end of the flexible
tip section;
at least one additional band electrode proximally spaced-apart from
the tip electrode on the flexible tip section;
a proximal connector housing fixedly attached to the proximal end
of the shaft;
whereby said shaft and said tip section provide torque transmission
directly from the housing to the tip electrode;
a core wire extending between the proximal connector housing and
the tip electrode and fixedly connected to both;
whereby said core wire provides torque transmission directly from
the housing to the tip; and
means for electrically connecting the electrodes to the proximal
connector housing.
15. An electrical potential reference catheter as in claim 14
wherein the shaft tube is composed of a material selected from the
group consisting of a polyurethane, a nylon, a polyethylene block
copolymer, and a polyolefin having a durometer from 35D to 75D with
a stainless steel reinforcement braid.
16. An electrical potential reference catheter as in claim 15,
wherein the tip tube is composed of a material selected from the
group consisting of a polyurethane, a nylon, a polyethylene block
copolymer, and a polyolefin having a durometer from 30A to 75A.
17. An electrical potential reference catheter as in claim 16,
wherein the core wire is stainless steel having a diameter from
0.005 in. to 0.025 in.
18. An electrical potential reference catheter as in claim 17,
wherein the core wire has proximal and distal ends, the core wire
being tapered, having a diameter from 0.015 in. to 0.025 in. at its
proximal end and a diameter from 0.005 in. to 0.015 in. at its
distal end.
19. An electrical potential reference catheter as in claim 14,
further comprising a polymeric sheath tube extending into an axial
receptacle in the tip electrode and receiving the core wire in
order to provide electrical insulation of the core wire at the
transition to the tip electrode.
20. An electrical potential reference catheter as in claim 19,
wherein the polymeric sheath tube is composed of a polyimide.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of
electrophysiology. More particularly, this invention relates to
methods and apparatus for mapping cardiac arrhythmias.
Symptoms of abnormal heart rhythm are generally referred to as
cardiac arrhythmias, with an abnormally slow rhythm being
classified as bradycardia and an abnormally rapid rhythm being
referred to as tachycardia. The present invention is concerned with
the treatment of tachycardias which are frequently caused by the
presence of an "arrhythmogenic site" or "accessory atrioventricular
pathway" close to the inner surface of one of the chambers of the
heart. The heart includes a number of normal pathways which are
responsible for the propagation of signals necessary for normal
electrical mechanical function. The presence of arrhythmogenic
sites or accessory pathways can bypass or short circuit the normal
pathways, potentially resulting in very rapid heart contractions,
referred to as tachycardias. Tachycardias may be defined as
ventricular tachycardias (VT's) and supraventricular tachycardias
(SVT's). VT's originate in the left or right ventricle and are
typically caused by arrhythmogenic sites associated with a prior
myocardial infarction. SVT's originate in the atria and are
typically caused by an accessory pathway.
Treatment of both ventricular and supraventricular tachycardias may
be accomplished by a variety of approaches, including drugs,
surgery, implantable pacemakers/defibrillators, and catheter
ablation. While drugs may be the treatment of choice for many
patients, they only mask the symptoms and do not cure the
underlying cause. Implantable devices only correct the arrhythmia
after it occurs. Surgical and catheter-based treatments, in
contrast, will actually cure the problem, usually by ablating the
abnormal arrhythmogenic tissue or accessory pathway responsible for
the tachycardia. The catheter-based treatments rely on the
application of various destructive energy sources to the target
tissue, including direct current electrical energy, radiofrequency
electrical energy, laser energy, and the like.
Regardless of the particular catheter-based treatment selected, it
will generally be necessary to initially map the interior surfaces
of the heart to locate the arrhythmogenic site(s) and accessory
pathway(s). Such mapping involves the measurement of electrical
potentials at different locations within the heart to detect
abnormalities using a procedure generally referred to as
"programmed electrical stimulation." A catheter having a series of
axially spaced-apart electrodes near its distal end is introduced
to the interior of the heart, and pacing of the heart is induced
using certain pairs of the electrodes, usually the distal pair.
Progression of the induced signal within the heart is monitored
using the remaining pairs of electrodes which are connected to
conventional ECG monitoring equipment. In this way, the locations
of the arrhythmogenic sites and accessory pathways can be generally
determined. Usually, the locations will be more specifically
determined prior to treatment using the treatment catheters
themselves. Treatment catheters are usually steerable and have
reference electrodes which can be more precisely positioned.
The reference electrode catheters used for ECG mapping have distal
tips which are shaped to lie in preselected configurations within
the heart chamber being mapped. It is thus necessary that the
distal tip of the catheter be manipulable from the proximal end so
that the distal tip can be properly oriented after it has been
introduced to the chamber. In particular, the treating physician
must be able to rotate the distal end of the catheter about its
longitudinal axis by applying a rotational torque to the proximal
end of the catheter. Thus, the reference electrode catheters must
be torsionally stiff to transmit the encessary rotational force
along their lengths. The ability to transmit torque along the
catheter, however, must be achieved without significant loss of
axial flexibility of the catheter, particularly at its distal end.
It will be appreciated that the distal end of the catheter should
remain soft and flexible in order to avoid injury to the heart.
Previous catheter designs have attempted to meet these objectives
but have not been completely satisfactory.
Thus, it would be desirable to provide improved reference electrode
catheters having enhanced torsional stiffness without significant
loss of axial flexibility, particularly at the distal tip region.
Such catheters should have a relatively simple construction, with a
reduced member of components and materials.
2. Description of the Background Art
A left ventricle mapping probe having a plurality of spaced-apart
band electrodes is described in U.S. Pat. No. 4,777,955. A cardiac
pacing catheter having a distal tip electrode and an electrically
conductive torque member in a central lumen filled with solid
polymer is described in U.S. Pat. No. 4,699,157. Intracardiac
catheters for recording monophasic action potentials in a heart and
including a distal tip electrode and one or more side electrodes
are described in U.S. Pat. Nos. 4,979,510; 4,955,382; and
4,682,603.
SUMMARY OF THE INVENTION
According to the present invention, an intracardiac electrical
potential reference catheter having enhanced torsional stiffness
and axial flexibility comprises a catheter body including both a
shaft section having a proximal end, a distal end, and a lumen
therethrough, and a flexible tip section having a proximal end, a
distal end, and a lumen therethrough. The proximal end of the tip
section is secured to the distal end of the shaft section so that
the lumens are generally coaxially aligned. A tip electrode is
secured to the distal end of the flexible tip section, and at least
one additional band electrode is mounted on the exterior of the tip
section spaced-apart proximally from the tip electrode. Usually, at
least two additional band electrodes will be disposed on the
flexible section, and as many as ten or more band electrodes may be
provided. The catheter further includes a proximal connector
housing secured to the proximal end of the shaft section, and the
tip and band electrodes are connected to an electrical connector
fitting on the housing, typically by wires running through the
lumens.
The torsional stiffness of the catheter is enhanced in two ways.
First, the shaft is a composite, comprising a polymeric tube
reinforced with a braided layer, typically being composed of a
thermoplastic material reinforced with a stainless steel braid.
Second, a core wire extends from the proximal housing through the
lumens of the shaft and the flexible tip sections, being fixedly
secured to both the proximal housing and to the distal tip
electrode. In this way, torque is efficiently transmitted to the
tip section both by the reinforced shaft section and by the core
wire which transmits torque directly from the proximal housing to
the distal electrode tip. Use of the core wire permits the flexible
tip section to be formed from a low durometer (soft) polymeric
material, without reinforcement, so that the tip may be axially
flexible while having sufficient torsional stiffness (from the core
wire) to permit the necessary torsional manipulation. By utilizing
a tapered core wire having a reduced diameter near its distal end,
the flexibility of the tip section can be further enhanced while
still providing adequate torque transmissibility.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an electrical potential reference
catheter constructed in accordance with the principles of the
present invention.
FIGS. 2A-2D illustrate various tip configurations of the electrical
potential reference catheter of FIG. 1.
FIG. 3 is a cross-sectional view of the distal portion of the
catheter of FIG. 1.
FIG. 4 is a cross-sectional view of a proximal housing of the
catheter of FIG. 1.
FIG. 5 is a transverse cross-sectional view of the distal end of
the catheter of FIG. 1, taken along line 5--5 of FIG. 3.
FIG. 6 is a transverse cross-sectional view of the distal end of
the catheter of FIG. 1, taken along line 6--6 of FIG. 3.
FIG. 7 is a transverse cross-sectional view of the shaft section of
the catheter of FIG. 1, taken along line 7--7 of FIG. 3.
DESCRIPTION OF SPECIFIC EMBODIMENTS
Referring to FIG. 1, an electrical potential reference catheter 10
constructed in accordance with the principles of the present
invention includes a flexible tip section 12 joined to a shaft
section 14 at an attachment point 16. The reference catheter 10 has
a distal end 18 and a proximal end 20, with an overall length
typically in the range from about 60 cm to 150 cm with lengths of
80 cm and 125 cm being usual for subclavian and femoral entry,
respectively. The flexible tip section 12 typically has a length in
the range from about 1 cm to 10 cm, usually being about 5 cm, with
the remaining length of the catheter being in the shaft section. A
proximal housing 22 is secured to the proximal end 20 of the
catheter 10.
A plurality of electrodes will be mounted on the tip section 12 of
the catheter 10 in order to permit ECG mapping in the conventional
manner. The electrodes will include a tip electrode 24 and at least
one proximally spaced-apart band electrode 26. Usually, at least
two additional band electrodes 28 and 30 will be provided, and the
catheter may include up to a total of 10 or more electrodes. The
spacing between electrodes is not critical, with adjacent
electrodes usually being spaced from 2 mm to 1 cm apart, typically
being about 5 mm apart. The spacing between adjacent electrodes may
be the same or different, with a variety of particular spacing
patterns being known in the art.
The distal portion of the catheter 10 will be shaped so that the
catheter will align in a preselected conformation after
introduction to a heart chamber. Usually, approximately 5 cm of the
distal end of the catheter 10 will be shaped, including the entire
flexible tip section 12 and a distal portion of the shaft section
14. As discussed below, both the flexible tip section 12 and shaft
section 14 will be usually formed from a thermoplastic material,
and shaping may be achieved by heating and molding in a
conventional manner. Conventional tip configurations are
illustrated in FIGS. 2A-2D, where the configuration of FIG. 2A is
useful for mapping the HIS bundle; the configuration of FIG. 2B is
useful for mapping according to the Josephson procedure; the
configuration of FIG. 2C is useful for mapping the coronary sinus;
and the configuration of FIG. 2D is useful for performing
conduction studies.
Referring now to FIGS. 1 and 3, the flexible tip section 12 of
catheter 10 comprises a polymeric tube 31 having a central lumen 32
extending therethrough. The polymeric tube 31 will be a low
durometer thermoplastic, typically being a polyurethane tube having
a durometer in the range from 30A to 75A and a wall thickness in
the range from about 0.005 in. to 0.030 in. A suitable polymeric
material for the flexible tip section 12 is Pellethane 2363
available from Dow Chemical Co., Midland, Mich. Other suitable
materials for the polymeric tube 31 include nylon, polyether block
copolymers (e.g., Peebax.RTM., Atochem, Germany), polyolefins
(e.g., Hytrel.RTM., DuPont, Wilmington, Del.), and the like. Tip
electrode 24 includes a bell-shaped distal section 34 and a shank
section 36, where the shank is received in the distal end of the
lumen 32 of the polymeric tube 30. Typically, the shank 36 is
secured by an adhesive. The electrode 34 may be formed from any
suitable electrode material, preferably being a platinum-iridium
alloy. Band electrodes 26, 28, and 30 are disposed on the outside
of the flexible tip section 12 and spaced proximally from the tip
electrode 24, and may also be composed of a platinum-iridium
alloy.
The shaft section 14 of catheter 10 is attached directly to the
proximal end of the flexible tip section 12, typically by heat
welding. The shaft section 14 comprises a polymeric tube 40 having
a central lumen 42 which is coaxial with the lumen 32 of the
flexible tip section 12. Polymeric tube 40 is reinforced with a
braided layer 44, typically a stainless steel braid, where the
braid characteristics, such as pick, angle, spacing, the nature of
the strand (i.e. flat or round), and the like, can be selected to
provide a desired torsional stiffness and axial flexibility. In an
exemplary embodiment, the braid is 304 LV stainless steel formed
from 0.003 in. diameter round strands at a 60.degree. to 65.degree.
braid angle.
The polymeric tube 40 will be composed of a thermoplastic,
typically having a hardness in the range from about 35 D to 75D.
Usually, the composite of the thermoplastic tube and braided layer
44 will be fabricated by placing a first tube over the braided
layer 44 and a second tube within the lumen of the braided layer,
and then heating the composite structure so that the thermoplastic
material impregnates the braid to form a unitary structure. An
exemplary polymeric material is polyurethane, such as Pellethane
2363. Alternatively, the tube 40 may be formed in a continuous
process where the thermoplastic is continuously extruded over the
braided layer 44. Other suitable materials for the polymeric tube
70 include nylon, polyether block copolymers (e.g., Peebax.RTM.,
Atochem, Germany), polyolefins (e.g., Hytrel.RTM., DuPont,
Wilmington, Del.), and the like.
Referring now to FIG. 4, the proximal housing 22 comprises an outer
shell 50 having an internal collet 52 which receives a strain
relief element 54. The proximal end 20 of the shaft 14 is received
within the strain relief element 54 and, in turn, is clamped within
the collet 52 and housing 50. Core wire 70 is fixed within the
proximal end 20 of the shaft 14, typically by an adhesive matrix
56. In this way, torque applied to the housing 22 is transmitted
directly to both the shaft 14 and to the core wire 42. The torque
is then transmitted separately by each of the shaft 14 and core
wire 42 through the length of the shaft and to the distal end 18 of
the catheter. Connecting wires 71 are attached to pins 78 which
form a connector plug at the proximal end of the housing 22.
A core wire 70 extends between the proximal housing 22 and the tip
electrode 34, and is fixedly secured at each end. In particular,
the core wire 70 is adhesively bonded in a sheath 72 disposed in a
receptacle 74 within the shank 36 of the tip electrode 24. The
polymeric sheath 72 provides an anchor point and electrical
insulation between the core wire 70 and the tip electrode 24.
The core wire 70 is typically a metal wire, usually being a
stainless steel wire having a diameter in the range from about
0.005 in. to 0.025 in. Preferably, the core wire 70 will be tapered
(in stages or uniformly along its length), with a diameter at the
proximal end in the range from 0.010 in. to 0.025 in. and at the
distal end in the range from 0.005 in. to 0.015 in. The core wire
70 serves to directly couple the proximal portion of shaft 14 to
the tip electrode 24 so that torque applied to the housing 22 will
be transmitted directly to the extreme distal tip of the catheter
10. In addition to torque transmission through the core wire 70,
the torque is also transmitted through the shaft section 14 of the
catheter to the proximal end of the flexible tip section 12. By
providing two separate torque transmitting elements within the
catheter 10, improved torque transmission from the proximal end to
the distal tip of the catheter is achieved without substantial loss
of axial flexibility, particularly within the flexible tip section
12.
The plug assembly 80 at the proximal end of housing 22 permits
connection of the catheter 10 to a standard ECG amplifier, such as
those commercially available from a supplier such as Gould, E4M,
and others. The connector 80 will include a number of pins
corresponding to the number of electrodes to permit proper
connection. Use of the catheter 10 and ECG mapping will be
performed in a generally conventional manner.
Although the foregoing invention has been described in detail for
purposes of clarity of understanding, it will be obvious that
certain modifications may be practiced within the scope of the
appended claims.
* * * * *